Forums

Q wrt Bluetooth, USB, RS232 and controllers

Started by bit eimer April 29, 2004
Hi all,

I'm new to this forum - hope to find some answers/help on the following:

I doing a project in which a laptop needs to communicate with a remote
PIC-based device.  I had originally planned to use RS232 at each end talking
through a pair of 900 MHz Linx transceivers.  Since this was to be a one-off
prototype, I kind of ignored the regulatory issues.

Now, I'm thinking that maybe I would like to switch to Bluetooth, primarily
because there should be no licensing/FCC approval required.  This approach
would also simplify the PC side since I could (I think) just use a USB-based
Bluetooth unit (like D-Link).  But on the PIC-based remote, I'm at a loss.
I've seen several "RS232 cable replacement" Bluetooth units that seem to
imply you just plug them in and you're done.  On the other hand, I see lots
of comments that suggest there's usually a fairly complicated s/w stack that
goes along with a Bluetooth module.  On the PC side, I assume that's just
the manufacturer-supplied driver's problem (or the OS's).  But I don't have
a clue what this means for my poor little PIC, or if its even feasible.

So I'm leary at this point, because I don't really want to become an expert
in Bluetooth profiles/protocols/whatever just to replace a straight-forward
RS232 link.

If anyone has tackle this issue and can provide some
hints/advice/suggestions, I sure would welcome it.

TIA,

-- 
...The Bit Eimer     [remove keinewurst to email me]

"My goal in life is to be the kind of person my cat thinks he is"
--------------------------------------------------------------



bit eimer wrote:
> > I doing a project in which a laptop needs to communicate with a > remote PIC-based device. I had originally planned to use RS232 > at each end talking through a pair of 900 MHz Linx transceivers. > Since this was to be a one-off prototype, I kind of ignored the > regulatory issues. > > Now, I'm thinking that maybe I would like to switch to Bluetooth, > primarily because there should be no licensing/FCC approval > required. ... snip ...
I suggest you start by defining the requirements, in terms of transfer rates needed, data volume, delays acceptable, etc. I also get the impression that wireless connection may not be essential. -- Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net) Available for consulting/temporary embedded and systems. <http://cbfalconer.home.att.net> USE worldnet address!
bit eimer wrote:
> Hi all, > > I'm new to this forum - hope to find some answers/help on the following: > > I doing a project in which a laptop needs to communicate with a remote > PIC-based device. I had originally planned to use RS232 at each end talking > through a pair of 900 MHz Linx transceivers. Since this was to be a one-off > prototype, I kind of ignored the regulatory issues. > > Now, I'm thinking that maybe I would like to switch to Bluetooth, primarily > because there should be no licensing/FCC approval required. This approach > would also simplify the PC side since I could (I think) just use a USB-based > Bluetooth unit (like D-Link). But on the PIC-based remote, I'm at a loss. > ...snip...
A couple of weeks ago I successfully used a Bluetooth module from Free2Move with a PIC. I even managed to reprogram the PIC via Bluetooth using an open source serial boot loader. See http://www.free2move.se/products.htm for a list of modules. The one I used was the F2M03AC2. These modules has the Bluetooth stack built-in. I think the F2M03AC cost just over $60 a piece. /us

"CBFalconer" <cbfalconer@yahoo.com> wrote in message
news:4091CDB8.7BF2FD0B@yahoo.com...

<snip>

> I suggest you start by defining the requirements, in terms of > transfer rates needed, data volume, delays acceptable, etc. I > also get the impression that wireless connection may not be > essential.
Burst data rate looks to be on the order of 4800 bits/sec, average rate very low. Not sure what you mean by "delays acceptable" unless you are referring to retransmit-induced latency as a result of detected errors. Didn't mean to imply that the wireless was not essential. Basic functionality can to shown/debugged with straight RS232 in the lab, but for field use wireless is crutial. Both laptop and remote unit will be mobile and independent. Having a wire between the two is not feasible. -- ...The Bit Eimer [remove keinewurst to email me] "My goal in life is to be the kind of person my cat thinks he is" --------------------------------------------------------------
This looks promising, although $60 seems on the high side, at least compared
to what you pay for a USB/Bluetooth "dongle" for the PC.    The website did
not show any sources in the US - where did you get your module?  Or are you
in Sweden?

So, does the code on the PIC deal with the Bluetooth module just as if it is
an RS232 device?

-- 
...The Bit Eimer     [remove keinewurst to email me]

"My goal in life is to be the kind of person my cat thinks he is"
--------------------------------------------------------------


"US" <me@nospam.com> wrote in message news:4091f623$1@news.wineasy.se...
> bit eimer wrote: > > Hi all, > > > > I'm new to this forum - hope to find some answers/help on the following: > > > > I doing a project in which a laptop needs to communicate with a remote > > PIC-based device. I had originally planned to use RS232 at each end
talking
> > through a pair of 900 MHz Linx transceivers. Since this was to be a
one-off
> > prototype, I kind of ignored the regulatory issues. > > > > Now, I'm thinking that maybe I would like to switch to Bluetooth,
primarily
> > because there should be no licensing/FCC approval required. This
approach
> > would also simplify the PC side since I could (I think) just use a
USB-based
> > Bluetooth unit (like D-Link). But on the PIC-based remote, I'm at a
loss.
> > ...snip... > > A couple of weeks ago I successfully used a Bluetooth module from > Free2Move with a PIC. I even managed to reprogram the PIC via Bluetooth > using an open source serial boot loader. > > See http://www.free2move.se/products.htm for a list of modules. The one > I used was the F2M03AC2. These modules has the Bluetooth stack built-in. > > I think the F2M03AC cost just over $60 a piece. > > /us
bit eimer wrote:
> This looks promising, although $60 seems on the high side, at least compared > to what you pay for a USB/Bluetooth "dongle" for the PC. The website did > not show any sources in the US - where did you get your module? Or are you > in Sweden?
Yes, I'm in Sweden, so I bought the modules directly from Free2move. Last year I bought their serial port dongle from Expansys. Maybe you could buy the modules as well from Expansys in the US?
> So, does the code on the PIC deal with the Bluetooth module just as if it is > an RS232 device?
That's right. I connected RXD, TXD directly to the PIC UART, and the CTS/RTS signals to some other i/o pins. They recommend that you use hw handshaking but I'm not sure you really need it. /us
"bit eimer" <bit_eimer.keinewurst@cox.net> wrote in message
news:yenkc.6765$k24.2050@fed1read01...
> This looks promising, although $60 seems on the high side, at least
compared
> to what you pay for a USB/Bluetooth "dongle" for the PC. The website
did
> not show any sources in the US - where did you get your module? Or are
you
> in Sweden? > > So, does the code on the PIC deal with the Bluetooth module just as if it
is
> an RS232 device? > > --
A device connected to the PC would have its protocol stack handled by the PC. So its brains would be the PC (which you pay hundreds for). This device which just transmits packetts and automagically connects to another Bluetooth device needs to have some smarts put in it to do that. I imagine the processor inside the bluetooth dongle would be more powerfull than the pic you want to connect to it. Tony
"Anthony Marchini" <amarchini@m_eri_k.anl0ckerd0t.com> wrote in message
news:Ertkc.2381$ph2.2342@fe39.usenetserver.com...

<snip>

> A device connected to the PC would have its protocol stack handled by the > PC. So its brains would be the PC (which you pay hundreds for). > This device which just transmits packetts and automagically connects to > another Bluetooth device needs to have some smarts put in it to do that. > I imagine the processor inside the bluetooth dongle would be more
powerfull
> than the pic you want to connect to it.
Good point. -- ...The Bit Eimer [remove keinewurst to email me] "My goal in life is to be the kind of person my cat thinks he is" --------------------------------------------------------------
"US" <me@nospam.com> wrote in message news:40924eaf$1@news.wineasy.se...

<snip>

> Yes, I'm in Sweden, so I bought the modules directly from Free2move. > Last year I bought their serial port dongle from Expansys. Maybe you > could buy the modules as well from Expansys in the US?
Yes, well kind of. The only Free2move unit they have is the packaged serial port device (at $142). They don't carry the bare module.
> > > So, does the code on the PIC deal with the Bluetooth module just as if
it is
> > an RS232 device? > > That's right. I connected RXD, TXD directly to the PIC UART, and the > CTS/RTS signals to some other i/o pins. They recommend that you use hw > handshaking but I'm not sure you really need it.
According to the Expansys website: "No external drivers are needed to use the plug. A user-friendly Windows application is included that can be used to configure the plug to suit your requirements. The software you have developed for your serial ports can remain unchanged when using the paired serial cable plugs. Windows software for configuring the Serial Port Plug is delivered for free." So according to this, while you don't need the s/w stack, you may need to do some setup/configuration (for which they provide the PC-side software). Did you have to develop some PIC code to do this config? If so, where did you get the techical info? Thanks again. -- ...The Bit Eimer [remove keinewurst to email me] "My goal in life is to be the kind of person my cat thinks he is" --------------------------------------------------------------
bit eimer wrote:
> ...snip... > According to the Expansys website: > > "No external drivers are needed to use the plug. A user-friendly Windows > application is included that can be used to configure the plug to suit your > requirements. > The software you have developed for your serial ports can remain unchanged > when using the paired serial cable plugs. Windows software for configuring > the Serial Port Plug is delivered for free." > > So according to this, while you don't need the s/w stack, you may need to do > some setup/configuration (for which they provide the PC-side software). Did > you have to develop some PIC code to do this config? If so, where did you > get the techical info?
By default, the module is configured as a slave waiting to be connected to. I didn't have to do anything special for my application other than setting the PIC UART to 38400 bps, which is the default setting for the BT module. I'm working on some config functions in C for the PIC. It's possible that Free2Move can offer some sample source code for the config protocol, I haven't asked them yet. For me the deciding factor was the small size of the Free2Move module. If size doesn't matter, you may want to consider the TDK modules. They have a small PCB where you can insert the module for configuration before integrating them with the target device. The Free2Move module I have used needs to be soldered onto a PCB to be accessible to anything (PC or PIC etc.) /us